家蚕β-1, 4-N-乙酰葡萄糖胺糖苷酶1基因（BmGlcNase1） 调控茧丝产量的分子机制研究

Silk production is the economic trait with great importance in sericulture. The comprehensive excellent breeds with higher silk production is the basis to upgrade this industry. And there is a larger demand of silkworm breeds with higher silk production at the coming era of industrialized and intelligent breeding. However, the improvement of silk production by traditional breeding methods has stepped into the platform for a long time. The further breakthrough on silk production improvement relies on molecular breeding to a large extent. Silk production related traits are the typical quantitative traits, controlled by multiple genes and the identification of genes underlying these traits has been proved to be challenge, which was rarely reported by now. Through genetic mapping and gene expression research, I, the applicant, identified that β-1,4-N-acetylglucosaminoglycosidase 1 (BmGlcNase1) is the candidate gene in locus controlling cocoon shell weight, an important index of silk production. Change of its expression level has a significant effect on this trait. Functional annotation showed that it is able to hydrolyze the β-1,4-glycoside bond and has the ability to regulate the N-hexosamine level. This project put efforts to elucidate the regulation mechanism of this gene on silk production, to research the new functions of genes related with N- glycosidylation in silk gland development and other processes in silkworm and to uncover their value in the molecular breeding of silkworm. Implementation of the project will advance our understanding on the genetic basis of silk production and the related biology issues, and will serve the reference for molecular breeding in silkworm.

茧丝产量是家蚕最受关注的经济性状，培育综合优良的高产品种是推动蚕丝产业升级的基础，尤其在工厂化、智能化养殖方式到来的时代具有迫切的现实需求。然而，传统育种对茧丝产量的提升已进入了平台期，其进一步突破在很大程度上寄希望于分子育种。茧丝产量为多基因支配，其控制基因的鉴定相对较难，至今鲜有报道。申请人前期通过分子定位主体策略，鉴定到β-1,4-N-乙酰葡萄糖胺糖苷酶1（BmGlcNase1）为茧丝产量控制位点候选基因，其表达变化显著影响茧丝产量的高低。该基因功能注释为水解β-1,4-糖苷键，参与N-己糖胺水平调节。本项目着力于阐释BmGlcNase1调控茧丝产量的分子机制，并探索N-己糖胺糖苷化的相关基因在丝腺发育等过程中的功能，揭示其在家蚕分子改良中的应用价值。项目的实施将促进对茧丝产量遗传调控及相关生物学问题的理解，并为家蚕分子育种提供理论参考。

蚕桑产业是我国特色优势产业，在脱贫攻坚中发挥了重要作用。茧丝产量是家蚕最受关注的经济性状，培育综合优良的高产品种是推动蚕丝产业升级的基础。然而，传统育种对茧丝产量的提升已进入了平台期，其进一步突破在很大程度上寄希望于分子育种。但茧丝产量为多基因支配，其控制基因的鉴定相对较难，至今鲜有报道。我们前期的数量遗传分析鉴定到β-1,4-N-乙酰葡萄糖胺糖苷酶1（BmGlcNase1）为茧丝产量控制位点候选基因，该基因功能注释为水解β-1,4-糖苷键，参与N-己糖胺水平调节。以此为基础，本项目进一步对其功能和影响茧丝产量的机制进行了研究，取得一系列重要研究成果及进展。主要包括：（1）通过遗传和基因功能研究证明了BmGlcNase1能够特异性影响中部丝腺发育，继而影响丝胶蛋白合成，最终影响茧丝产量。并通过人工选择特征分析揭示了在家蚕驯化和育种改良过程中，蚕茧丝蛋白组成在BmGlcNase1参与下的变化过程。这一部分发表于国际遗传学著名杂志PLoS Genetics。（2）鉴定到几丁质β-己糖胺糖苷酶基因Chit β-GlcNAcase能影响吐丝器构建，进而影响茧丝纤度。并发现其在家蚕变态和翅膀发育中发挥重要作用。该部分结果发表于国际分子生物学知名杂志International Journal of Molecular Sciences。（3）发现多个己糖胺代谢通路相关基因在家蚕驯化过程中受到选择，且部分基因在丝腺中表达水平较高。此外，鉴定到多个己糖胺代谢通路相关基因在不含几丁质的组织中高表达，表明该通路基因广泛参与其他分子过程，并影响昆虫组织及个体发育。（4）项目还在前期QTL定位的基础上，对另外两个CSW位点（csw1和csw2）的控制基因进行了鉴定。其中针对csw1的精细定位鉴定到多个成簇分布的基因共同贡献了该位点显著的遗传效应。针对csw3的遗传研究鉴定到Bmelo2为该区域控制茧丝产量的基因。本部分结果已撰文发表于遗传学著名杂志Journal of Genetics and Genomics。本项目所获得的成果对于理解茧丝产量的遗传基础和推进其分子改良具有重要意义。